diff --git a/src/RMHD_converter.cpp b/src/RMHD_converter.cpp
index 222f7ec063cc2b6b10c29cff6819baffbf16426b..793b05082d35e788f48c7669fbb4fa2c21c1c80f 100644
--- a/src/RMHD_converter.cpp
+++ b/src/RMHD_converter.cpp
@@ -98,9 +98,9 @@ RMHD_converter::~RMHD_converter()
 }
 
 int RMHD_converter::convert(
-        const char *ifile0,
-        const char *ifile1,
-        const char *ofile)
+        char *ifile0,
+        char *ifile1,
+        char *ofile)
 {
     //read first field
     this->f0c->read(ifile0, (void*)this->c0);
diff --git a/src/RMHD_converter.hpp b/src/RMHD_converter.hpp
index 6ce834c6f0f912ebfff24775d3ece70c84081129..ebb1b00c1876680e30a8383bcf51aeed50a48004 100644
--- a/src/RMHD_converter.hpp
+++ b/src/RMHD_converter.hpp
@@ -41,9 +41,9 @@ class RMHD_converter
         ~RMHD_converter();
 
         int convert(
-                const char *ifile0,
-                const char *ifile1,
-                const char *ofile);
+                char *ifile0,
+                char *ifile1,
+                char *ofile);
 };
 
 #endif//RMHD_CONVERTER
diff --git a/src/field_descriptor.cpp b/src/field_descriptor.cpp
index 2e1396b2246bb5049f77625bcdf31772fc550c1c..61d1134789c7ec587f728dba838baa4532c567b4 100644
--- a/src/field_descriptor.cpp
+++ b/src/field_descriptor.cpp
@@ -3,8 +3,6 @@
 #include <iostream>
 #include "field_descriptor.hpp"
 
-extern int myrank, nprocs;
-
 field_descriptor::field_descriptor(
         int ndims,
         int *n,
@@ -79,7 +77,7 @@ field_descriptor::~field_descriptor()
 }
 
 int field_descriptor::read(
-        const char *fname,
+        char *fname,
         void *buffer)
 {
     MPI_Info info;
@@ -111,7 +109,7 @@ int field_descriptor::read(
 }
 
 int field_descriptor::write(
-        const char *fname,
+        char *fname,
         void *buffer)
 {
     MPI_Info info;
@@ -268,7 +266,7 @@ field_descriptor* field_descriptor::get_transpose()
     return new field_descriptor(this->ndims, n, this->mpi_dtype, this->comm);
 }
 
-void proc_print_err_message(const char *message)
+void proc_print_err_message(char *message)
 {
     for (int i = 0; i < nprocs; i++)
     {
diff --git a/src/field_descriptor.hpp b/src/field_descriptor.hpp
index 271d3d8e243f42f1f0c5389ab350e134e21cae2a..905843c3b33054cbfdfa4688d92f082c0b5a2bfc 100644
--- a/src/field_descriptor.hpp
+++ b/src/field_descriptor.hpp
@@ -5,6 +5,8 @@
 
 #define FIELD_DESCRIPTOR
 
+extern int myrank, nprocs;
+
 class field_descriptor
 {
     public:
@@ -33,10 +35,10 @@ class field_descriptor
          * own mpi_array_dtype that was defined in the constructor.
          * */
         int read(
-                const char *fname,
+                char *fname,
                 void *buffer);
         int write(
-                const char *fname,
+                char *fname,
                 void *buffer);
 
         /* a function that generates the transposed descriptor.
@@ -80,7 +82,7 @@ int fftwf_clip_zero_padding(
         field_descriptor *f,
         float *a);
 
-void proc_print_err_message(const char *message);
+void proc_print_err_message(char *message);
 
 #endif//FIELD_DESCRIPTOR